Recently, a fuel cell using hydrogen and oxygen is attracting attention as a power source. During start-up of the fuel cell, supply of hydrogen to an anode channel is started, and air inside the anode channel is substituted with hydrogen. During this process of the air inside the anode channel being substituted with hydrogen, an oxidation-reduction reaction is carried out at a region A at the inlet side of the anode channel which is filled with hydrogen and at a region B at the outlet side thereof which is filled with air.
With this oxidation-reduction reaction, electromotive force is generated at the region A and the region B, platinum in a catalyst layer of the cathode exhibits high potential by the potential difference between the region A and region B, which encourages elution of the platinum, so that electrolyte membrane becomes deteriorated.
Therefore, there is proposed a technique of suppressing deterioration of the electrolyte membrane by reprecipitating platinum flowing out from the catalyst layer of the cathode, by maintaining potential of the cathode at 0.6V or less for a predetermine time or more, when it is determined during start-up of the fuel cell that the interior of the anode channel is filled with hydrogen (for example, refer to Japanese Patent Laid-Open 2009-64681).